To process a batch of wafers in a furnace, the wafers can be loaded into a wafer boat in a vertically stacked and spaced manner. The wafer boat can have the design shown in FIG. 1. The wafer boat is indicated in its entirety by reference numeral 100. The wafer boat 100 is typically formed of quartz but can also be formed of other materials, such as silicon carbide or other ceramic materials. Three or more vertically-extending rods 102, 103 and 104 are each attached at their upper and lower ends, respectively, to a top plate 105 and a bottom plate 106. Vertically spaced recesses 110 are formed at similar heights in each of the rods 102, 103, 104 with the remaining material of the rods 102, 103, 104 forming ridges which can function as wafer or substrate supports. The corresponding recesses 110 at the same height in each of the wafer rods 102, 103, 104 collectively form an accommodation for a wafer in which the wafer is supported at an edge portion thereof by the wafer support ridges. Wafers are loaded into and unloaded out of the accommodations from an open side 107, where a robot can access the wafers without any rods interfering with the movement of wafers into or out of the wafer accommodations.
After loading wafers into the boat 100, the boat 100 is loaded into the process chamber of a hot furnace for processing in the furnace. After processing in the furnace is completed, the hot wafer boat is unloaded from the furnace. After a cool-down period, the wafers are unloaded from the wafer boat by a wafer handling robot.
An effect that can occur during wafer processing, which includes the period during which wafers are handled before and after being processed in the process chamber, is the formation of particles on the wafers. For example, during a low pressure chemical vapor deposition (LPCVD) process to form silicon nitride, particle formation occurs on semiconductor wafers held in a quartz boat having a design such as that shown in FIG. 1. It will be appreciated that particle formation on the wafers is undesirable because the particles can detrimentally affect the performance of semiconductor devices formed on the wafers.
Consequently, there is a need for a substrate processing systems and methods that minimize particle formation during semiconductor substrate processing.